Soft vinyl chloride resin materials and RIM urethane materials, both of which are injection moldable, have widely been used in recent years as a soft skin material of a steering wheel for motor vehicles. In particular, the RIM urethane materials predominate in the skin material for steering wheels because of their good wear resistance and imparting soft touch.
However, the RIM urethane materials have such problems that a cycle for molding is long, it takes a long time for a post-treatment processing, and have problems in view of recycling the scrap molded articles thereof such that RIM urethane materials cannot be melt again because they are thermoset resins.
Furthermore, the soft vinyl chloride resin materials have problems of a high specific gravity and generation of chlorine gases when heated for recycling the scrap molded articles thereof.
Therefore, a soft, recyclable injection molding material having a low specific gravity has been desired as a skin material of a steering wheel for motor vehicles. For the materials as described above, thermoplastic olefin elastomers are suitable.
However, conventional thermoplastic olefin elastomer materials have not been used as the skin material of the steering wheel for the motor vehicles because they are low in wear resistance that is an essential requirement for the skin material of the steering wheel for the motor vehicles.
With this respect, the present inventors have earnestly studied to obtain an injection-moldable soft thermoplastic olefin elastomer material having a low specific gravity and good wear resistance, which is capable of recycling and gives good feel of touch, and have found that a thermoplastic elastomer composition containing a polyethylene resin and a styrene block copolymer at a particular proportion has the above mentioned properties or effects. The present invention was thus completed.
The present invention was made to solve the problems associated with the conventional arts as described above, and an object thereof is to develop an injection-moldable soft thermoplastic olefin elastomer composition having a low specific gravity and excellent wear resistance, which is capable of recyling and gives good feel of touch, and to provide a steering wheel for motor vehicles of which skin material is made of that composition.